This invention relates to a method of preparing a composition for controlled release of active materials. More specifically, it relates to a method of preparing a polyhydroxy polymer/borate/salt composition with active materials contained within the matrix.
Polyhydroxy polymers such as polyvinyl alcohol (PVA) are known to react with borates to form water insoluble crosslinked polymers. Japanese Pat. No. 74/48073 describes the use of borax to harden PVA used in the form of micro-capsules to encapsulate perfume and flame retardants. South African Pat. Nos. 69/00122 and 69/00088 disclose the use of PVA-borate capsules for plasticizers and dyes. U.S. Pat. No. 4,110,431 discloses the use of polyvinyl alcohol-borate complexes formed by water activation of mixtures of the PVA and borax in situ for attaching plant treatment additives to plant foliage. U.S. Pat. No. 4,440,746 discloses that PVA can be converted into granular matrices with controlled release properties by reacting PVA/pesticide emulsions or dispersions with borates. Also, U.S. Pat. No. 4,439,488 discloses the reaction of starch or PVA pastes at alkaline pH with boric acid or boric acid derivatives to form an insolubilized gel matrix in which chemical biological agents such as pesticides can be entrapped for controlled release applications.
It is also known that polyhydroxy polymers such as polyvinyl alcohols can be coagulated from aqueous systems by the addition of various salts. French Pat. No. 1,304,891 describes a process for converting PVA into microcapsules by treating PVA/dye emulsions with inorganic sulfates.